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Scientists comment on the continuing hantavirus situation aboard a cruise ship.
Dr Giulia Gallo, Postdoctoral Scientist in the Viral Glycoproteins Group, The Pirbright Institute, said:
How is hantavirus treated? Is there any specific treatment? If not, how may doctors try to treat it?
“Currently, there are no vaccine or antivirals approved for the treatment of hantaviruses. If the disease progresses and affects the lungs, patients are treated in ICU to provide respiratory support, such as mechanical ventilation, and general medication to reduce fever and maintain appropriate blood pressure. Cases have been reported of people in the febrile phase who did not develop any lung-associated severe phase.
Do we know how hantavirus could spread between humans? Is it through bodily fluids, or is it airborne, or do we not know?
“We know very little about human-to-human spread of hantavirus. Currently, only Andes virus, a species belonging to the hantavirus family, has been reported for transmission among people. It is believed that transmission can occur through inhalation of viral particles from an infected patient, in cases of close proximity such as being a sexual partner, kissing, and sleeping in the same room during the febrile phase of the disease. Nosocomial transmission (within hospital) has also been reported, although it is considered rare. Currently, we do not know how long or frequent the exposure needs to be for transmission to occur, as only few cases have been described in the literature.
Is it likely that the virus is already in the UK? (even if it is not connected to this outbreak)?
“Andes virus is not endemic in the UK. In Europe and Asia, what we classified as Old World hantaviruses have been found, while Andes is a New World hantavirus. This distinction is geographical, but it also reflects the type of diseases and pathogenicity in humans. Old World hantaviruses cause a fever with renal syndrome, which as the name says, mainly affects the kidneys. The fatality rate varies between 1 to 15%, so lower than reported for viruses such as Andes. New World hantaviruses cause a disease called Pulmonary syndrome, because it mainly debilitates the lungs.
What is the worst case scenario? What’s the danger of the virus spreading off the ship, considering a Swiss patient who disembarked in South America is now hospitalized in Zurich?
“I think that considering the attention that the story is getting, the risk of the virus spreading is very low. Authorities are already tracing potential contacts that might have happened between passengers that disembarked the ship and the rest of the population.
Is it possible passengers will be stuck on the cruise for 2 months due to the virus’s incubation period?
“I hope they will be transported to an appropriate centre where they could isolate in better conditions and where ICU support could be rapidly provided, were they to develop serious hantavirus-related symptoms. This should be a priority for the authorities, alongside with testing of passengers to detect any additional potential infected patient(s). Hopefully, this can be organised quickly, in less than 2 months.
If the ship is allowed to dock at the Canary Islands, what is likely to happen next? Will they do blood tests on all passengers to check for asymptomatic infections?
“It is hard to predict what is going to happen – screening for the presence of viral genome/antibodies and quarantine should be prioritized for all passengers. In case other persons have been exposed to the virus, these measures would allow for a rapid reaction from the health authorities.
How long is the turnaround time for the test results?
“If prioritised and pipelines for diagnosis are already in place, these analysis are relatively quickly, and results should be expected in few hours.
Does the Andes strain mutate frequently in ways that could increase its transmissibility between humans?
“We know very little about how this virus could evolve – a few papers have investigated the matter, and concluded that hantaviruses mutate and evolve at a similar rate compared to other RNA viruses. Unfortunately, we do not have any precise information about the specific case of Andes, especially regarding human-to-human transmission.”
Prof Rowland Kao, Professor of Veterinary Epidemiology and Data Science, Royal (Dick) School of Veterinary Studies, University of Edinburgh, said:
“The incubation period for Andes virus in humans is very long (listed as 9 to 40 days) which would suggest that, long after infection there will be some risk of onward transmission. As you know, Andes virus is also unusual in that the evidence is that human-to-human transmission can occur in conditions of very close contact. However because it is only close contact, the overall risk to the general public is itself very low, and the probability of sustained transmission from person-to-person therefore even lower. So while anyone who has been on the affected ship should be aware of the symptoms, and get tested should they display it, for anyone other than a potential close contact, the risks are negligible.
“The main risk of it coming onshore by other means, is through infected rodents (i.e. if transmission occurred via infected rodents on the cruise ship), however reports suggest it is more likely that transmission and infection occurred from rodents onshore either before the cruise or during one of the stops during its itinerary in the South Atlantic – if so, the long incubation period means that this might be difficult to identify precisely where it occurred. While there is no evidence reported of infected rodents on this ship (and it is likely that they have looked very carefully), more generally rodents are the most likely way this disease could spread to new regions.”
Dr Charlotte Hammer, Assistant Professor and infectious disease epidemiologist, University of Cambridge, said:
“Given the geography, the Andes strain of New World Hantaviruses was already the most likely causative agent in this case. This also explains the possibility of limited human-to-human transmission among very close contacts which has in the past been reported with this strain specifically. Given the incubation period of one to eight weeks, an initial infection before boarding the ship of some or all affected individuals seems likely. To what degree human-to-human transmission then happened remains to be determined. Further investigations into the initial exposure and the links between the cases would be helpful to clarify the transmission.”
Prof Sir Andrew Pollard FRCPCH FMedSci FRS, Ashall Professor of Infection and Immunity, Pandemic Sciences Institute, and Director of the Oxford Vaccine Group, University of Oxford, said:
“Identification of the virus as Andes virus strain of hantavirus by the South African infectious disease laboratory is helpful as the public health authorities now know exactly what they are dealing with. This means that the risks of transmission to contacts, including healthcare workers, from cases is known and can be managed by standard protocols. It also means that the “incubation period” is known – the time from exposure to developing symptoms – so that those who have been potentially exposed can be monitored and treated early and isolated if they become unwell. With these public health measures rigorously in place, the risk of onward transmission to the wider community should be essentially zero.”
Prof Paul Hunter, Professor in Medicine, UEA, said:
“The finding of the Andes variant strengthens the hypothesis that the initial cases were acquired in Argentina. This is endemic in Argentina and its host is the Long-tail pygmy rice rat, which as far as I know does not occupy ships, though I am not an expert on rats in ships. The question remains how this infection then spread to the later cases.”
Dr Michael Head, Senior Research Fellow in Global Health, University of Southampton, said:
“There are emerging reports that this is the Andes strain of hantavirus, with laboratory tests ongoing. There have been documented cases of human-to-human transmission from the Andes strain. For example in one outbreak in Argentina, there was a single environmental exposure to rodents and three symptomatic patients then infected others at crowded social events, resulting in 34 cases and 11 deaths.
“Whilst definitely plausible, we still do not know for sure if there is human-to-human transmission in this hantavirus outbreak. The period of time between initial infection and developing symptoms, the incubation period, can be several weeks.
“Thus, the case in Switzerland could be related to an exposure from their travels in South America in late April.”
Ref, Andes strain of hantavirus and transmission – https://www.nejm.org/doi/full/10.1056/NEJMoa2009040
Comments sent out about this hantavirus situation on Tuesday 5 May and Monday 4 May:
Declared interests
Dr Giulia Gallo: “I have no conflict of interest.”
Prof Rowland Kao: “I have no competing interests.”
Dr Charlotte Hammer: “I have no interests to declare.”
Prof Sir Andrew Pollard: “Nothing I can think of for hanta.”
Prof Paul Hunter: “No COIs.”
Dr Michael Head: “No COI.”